1. Field
The present embodiments relate to an allocation control apparatus for controlling an allocation of storage capacity of an entire storage system that has a plurality of storage devices and a method thereof.
2. Description of the Related Art
Conventionally a technique has been put to practical use that pools capacity of disks in a storage device, and creates and provides a logical disk based on a client request. A characteristic of the technique includes a provisioning. The provisioning is a function that does not allocate all of storage capacity to a disk (virtual disk) when creation of a logical disk is requested, but allocates storage capacity when a client accesses the disk.
The technique allows creating a logical disk that exceeds a capacity of a disk pool or more. If the remaining capacity of a disk pool decreases as a result of increase in allocation of storage capacity in response to accesses from clients, the disk pool may be extended by connecting a new disk.
In order to achieve a provisioning function, a storage device needs to have the following functions in addition to a function to perform accesses; a function to manage a logical capacity of a logical disk and to manage allocated storage capacity a function to allocate a disk pool to the logical disk at a timing when a client accesses, and a function to notify an available capacity of the disk pool.
A storage device that supports conventional provisioning is configured in which a single control apparatus connects clients and a disk pool, and the control apparatus provides the above functions. Thus, there are drawbacks in that the numbers of clients and disks that can be connected to the single control apparatus are limited, thus the scalability is limited.
Under these circumstances, a multi-node system with high scalability has been put to practical use in order to build a large scale virtual storage system (for example, Japanese Laid-open Patent Publication No. H. 9-311810, International Publication 2004/104845, Japanese Laid-open Patent Publication No. 2007-122463). The multi-node system is configured by connecting a plurality of disk nodes that include general purpose disk devices and servers via a network.